In recent years, in processes for assembling and producing various industrial products and home electronics, and processes for producing various devices (e.g., electronic components, batteries and substrates) that can be components included in such industrial products and home electronics, paste materials that have various functions are coated onto the products or devices, and then, the products or devices are subjected to heat treatments by use of various heat treatment apparatuses. For example, the heat treatment apparatuses include drying furnaces, baking furnaces, cure furnaces, and reflow furnaces. Reflow furnaces are used for, for example, soldering in an electronic component-mounting process. Various solvents such as water and organic solvents are mixed into the paste materials, according to their purposes or as needed, in addition to solid contents required in final products, in order to coat the paste materials onto various substrates or base materials, and thus, the viscosities or performance of the paste materials are adjusted.
The solvents included in the paste materials are released from the paste materials inside the heat treatment apparatuses through the vaporization and solvent-removing processes in heating steps carried out in the heat treatment apparatuses. Accordingly, in cases where the heat treatments are continuously carried out, the solvents are vaporized and released from the paste materials inside the apparatuses, and, as a result, the concentrations of the vaporized solvents inside the heat treatment apparatuses are increased. Such increases in the concentrations of the vaporized solvents inside the heat treatment apparatuses possibly cause various problems. For example, with increasing concentrations of the solvents in the atmospheres inside the heat treatment apparatuses, allowable amounts of solvents in the atmospheres at temperatures inside the apparatuses come close to saturation, and thus, it may be difficult to dry the object that is subjected to the heat treatment. Additionally, in cases where explosive solvents are used, the concentrations of the vaporized solvents possibly exceed limits for explosion even if the concentrations do not reach the saturated steam pressures. Therefore, it is required to regularly or continuously supply the outside air into the heat treatment apparatuses from the outside, and also, it may be required to regularly or continuously supply a nitrogen gas or any other atmospheres (atmosphere gases) into the heat treatment apparatuses from the outside, as needed. Furthermore, simultaneously, any means for releasing to the outside the atmospheres that are present inside the heat treatment apparatuses and that include increased concentrations of the solvents may be required.
FIG. 8 is a diagram that depicts supply and discharge of an atmosphere. The outside air is supplied into a heat treatment apparatus 1 with a blower 2. A part of the atmosphere present inside the heat treatment apparatus 1 and including a solvent vaporized in the heat treatment apparatus 1 is discharged to the outside with a blower 3. As an example of a system for removing the vaporized solvent included in an exhaust gas, a system disclosed in JP-A-2015-142898 is known.
FIG. 9 is a schematic diagram that shows a structure of the system disclosed in JP-A-2015-142898. The structure disclosed in JP-A-2015-142898 is as follows. An electrode 6 is provided on a first wall surface 5a in a solvent separation unit 4, and a voltage can be applied to the electrode 6 from a voltage-applying apparatus 7. Furthermore, a second wall surface 5b opposing the first wall surface 5a is insulated from the electrode 6, and is connected to a grounding wire. The outlet side of the solvent separation unit 4 is configured so as to branch into a first exhaust duct 8 and a second exhaust duct 9, and the first exhaust duct 8 is provided so as to extend from the first wall, surface 5a. By adopting such a structure, a difference in potentials is caused between the second wall surface 5b and the first wall surface 5a opposing the second wall surface 5b, and thus, an electric field 10 is formed inside the solvent separation unit 4. Accordingly, a solvent 11 included in an exhaust atmosphere 12 that has been discharged from the heat treatment apparatus 1 and that has been supplied into the solvent separation unit 4 is attracted toward the electrode 6 due to electrostatic attraction when the solvent 11 reaches an effective region of the electric field 10. Thus, a first exhaust atmosphere 13 that includes the solvent 11 collected at the side of the electrode 6 is discharged from the first exhaust duct 8, while a second purified exhaust atmosphere 14 that does not include the solvent 11 is discharged from the second exhaust duct 9.